The present invention relates to a method for analyzing amino acids of a biological liquid and an apparatus therefor.
In an apparatus for analyzing amino acids included in biological liquids, for example, urine and blood serum, efforts for improving separation performance of three components, asparagine, glutamine acid and glutamine, have been continued as disclosed in Japanese Laid-open Patent Publication Sho-59-10,849(1984) and U.S. Pat. No. 4,133,735. In separating about forty amino acid components in the biological liquids, in order to improve the separation performance of the three components which are most important and most difficult to be separated, some analysis method have been proposed, for example, refinement of filler (ion exchange resin) in the separation column, improvement of buffer liquid composition used as separation liquids, and change of the temperature of the separation column. However, every method can not satisfy the requirements completely.
FIGS. 1 and 2 are chromatograms of a mixed reference liquid corresponding to biological liquids including the following forty-two amino acids.
TABLE ______________________________________ Names of amino acids ______________________________________ C1 phosphoserine C2 taurine C3 urea C4 aspartic acid C5 hydroxyproline C6 threonine C7 serine C8 asparagine C9 glutamic acid C10 glutamine C11 sarcosine C12 .alpha.-amino adipic acid C13 proline C14 glycine C15 alanine C16 citrulline C17 .alpha.-amino-n-butyric acid C18 valine C19 cysteine C20 methionine C21 d,1-cystathionine C22 ios-leucine C23 leucine C24 nor-leucine C25 tyrosine C26 phenylalanine C27 .beta.-alanine C28 .beta.-amino-iso-butyric acid C29 homoscysteine C30 .gamma.-amino-iso-butyric acid C31 tryptophan C32 ethanolamine C33 ammonia C34 d,1-hydroxylysine C35 ornithine C36 histidine C37 1-methylhistidine C38 lysine C39 3-methylhistidine C40 anserine C41 carnosine C42 arginine ______________________________________
The chromatogram shown in FIG. 1 is obtained by using a new separation column and the other one shown in FIG. 2 is obtained by using an old separation column which has been used in the measurement of about five hundred blood serum samples.
In FIG. 1, peaks indicative of asparagine 21, glutamine acid 22, and glutamine 23 are separated clearly. On the contrary, in FIG. 2, the asparagine 21a and the glutamine acid 22a are not clearly separated and a valley between the two peaks disappears. As a result, both the peaks are calculated as an one peak in the calculation process of the peak area and the apparatus decides that there is no peak indicative of the asparagine 21a.
When the above situation occurs, an operator makes a decision that there is no reliability of qualitative analysis and quantitative analysis on all components because of termination of available time period and changes the separation column to a new one. The frequent exchange of the separation column makes running cost of the analysis up, and therefor, extension of the available time has been desired.